Method for making three-dimensional porous composite structure

ABSTRACT

A three-dimensional porous composite structure comprises a porous structure and at least one carbon nanotube structure. The porous structure has a plurality of metal ligaments and a plurality of pores. The at least one carbon nanotube structure is embedded in the porous structure and comprising a plurality of carbon nanotubes joined end to end by van der Waals attractive force, wherein the plurality of carbon nanotubes are arranged along a same direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 fromChina Patent Application No. 201710317874.3, filed to May 8, 2017 in theChina Intellectual Property Office, the disclosure of which isincorporated herein by reference. The application is also related tocopending U.S. applications entitled, “THREE-DIMENSIONAL POROUSCOMPOSITE STRUCTURE”, Ser. No. 15/792,790 filed Oct. 25, 2017; “ANODE OFLITHIIUM ION BATTERY AND LITHIUM ION BATTERY USING THE SAME”, Ser. No.15/792,792 filed Oct. 25, 2017; “FUEL CELL ELECTRODE AND FUEL CELL USINGTHE SAME”, Ser. No. 15/792,793 filed Oct. 25, 2017; and “BIOSENSORELECTRODE AND BIO SENSOR USING THE SAME”, Ser. No. 15/792,795 filed Oct.25, 2017.

FIELD

The subject matter herein generally relates to a method for makingthree-dimensional porous composite structure.

BACKGROUND

Nanoporous metal materials not only have high specific surface area,specific modulus and other characteristics, but also have a high thermalconductivity, high conductivity and other characteristics of metalmaterials, and have been widely used in a plurality of fields such ascatalysis, energy storage and transformation, biosensor, moleculardetection, silence vibration, shielding, heat exchange,electrochemistry.

In general, the nanoporous metal materials are often used in form of ananoporous metal composite. However, the nanoporous metal materials arecomposited with other materials by a binder, which increases internalresistance of the nanoporous metal composite. Further, the nanoporousmetal materials are very fragile. Therefore, a conductivity of thenanoporous metal composite is low, and a strength of the nanoporousmetal composite is poor, which limit the application of the nanoporousmetal composite.

What is needed, therefore, is to provide a method for makingthree-dimensional porous composite structure which can overcome theshortcomings as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a schematic view according to one embodiment of thethree-dimensional porous composite structure.

FIG. 2 is a Scanning Electron Microscope (SEM) image of a plurality ofcarbon nanotubes locating in a pore in the three-dimensional porouscomposite structure.

FIG. 3 is a flow chart of a method for making the three-dimensionalporous composite structure.

FIG. 4a is a Scanning Electron Microscope (SEM) image ofthree-dimensional porous composite structure obtained by chemicalcorrosion of 0.05 g/L dilute hydrochloric acid.

FIG. 4b is a Scanning Electron Microscope (SEM) image of cross-sectionof the three-dimensional porous composite structure in FIG. 4 a.

FIG. 5 is a Scanning Electron Microscope (SEM) image of thethree-dimensional porous composite structure obtained by electrochemicalcorrosion of 0.05 g/L dilute hydrochloric acid.

FIG. 6 is a Scanning Electron Microscope (SEM) image of thethree-dimensional porous composite structure at a low magnification.

FIG. 7 is a Scanning Electron Microscope (SEM) image of thethree-dimensional porous composite structure obtained by chemicalcorrosion of 0.05 g/L dilute hydrochloric acid for fifteen hours.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The connection can be such that the objects are permanently connected orreleasably connected. The term “substantially” is defined to beessentially conforming to the particular dimension, shape or other wordthat substantially modifies, such that the component need not be exact.The term “comprising” means “including, but not necessarily limited to”;it specifically indicates open-ended inclusion or membership in aso-described combination, group, series and the like. It should be notedthat references to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

The present disclosure relates to a three-dimensional porous compositestructure described in detail as below.

Referring to FIG. 1 and FIG. 2, a three-dimensional porous compositestructure according to one embodiment is provided. The three-dimensionalporous composite structure is a three-dimensional network structure. Thethree-dimensional porous composite structure includes a porous structureand at least one carbon nanotube structure. The at least one carbonnanotube structure is embedded in the porous structure.

The porous structure includes a plurality of metal ligaments. Theplurality of metal ligaments define a plurality of pores. Each of theplurality of pores is formed by adjacent metal ligaments. The pluralityof pores can be regularly distributed or irregularly distributed. Sizeof the plurality of pores are less than or equal to 100 micrometers. Themetal ligaments can be made of inert metal materials. Examples of theinert metal materials comprise copper (Cu), silver (Ag), platinum (Pt)and aurum (Au).

The carbon nanotube structure includes a plurality of carbon nanotubescombined by van der Waals force therebetween. The carbon nanotubestructure has good mechanical strength, toughness and conductivity. Thecarbon nanotube structure further includes a plurality of micropores.The plurality of micropores can be defined by adjacent carbon nanotubesin the carbon nanotube structure.

When the three-dimensional porous composite structure includes aplurality of carbon nanotube structures, the plurality of carbonnanotube structures can be spaced from each other. An angle θ betweencarbon nanotubes in adjacent spaced carbon nanotube structures can beranged from 0° to 90°.

The carbon nanotube structure can be an ordered carbon nanotubestructure. The term ‘ordered carbon nanotube structure’ refers to astructure where the carbon nanotubes are arranged in a consistentlysystematic manner, e.g., the carbon nanotubes are arranged approximatelyalong a same direction. The carbon nanotube structure includes at leastone carbon nanotube film. The carbon nanotube film can be a drawn carbonnanotube film.

The drawn carbon nanotube film includes a plurality of successive andoriented carbon nanotube segments joined end-to-end by van der Waalsforce therebetween. The drawn carbon nanotube film is a free-standingfilm. The drawn carbon nanotube film can be obtained by drawing from acarbon nanotube array substantially along a same direction. The carbonnanotube film has good mechanical strength, toughness and conductivity.

If the carbon nanotube structure includes a plurality of carbon nanotubefilms, the plurality of carbon nanotube films can be coplanar orstacked. An angle a between carbon nanotubes in adjacent stacked carbonnanotube films can be ranged from 0° to 90°.

The at least one carbon nanotube film are embedded in the porousstructure. One part of the carbon nanotubes in the carbon nanotube filmare embedded in the metal ligament, and another part of the carbonnanotubes in the carbon nanotube film are located in the plurality ofpores, and/or the others part of the carbon nanotubes in the carbonnanotube film are exposed from surface of the porous structure.

The three-dimensional porous composite structure has the followingadvantages: the carbon nanotube structure is embedded in the porousstructure, the three-dimensional porous composite structure has goodelectrical conductivity, toughness and stability; and has a largespecific surface area; the carbon nanotubes as a strengthen structureare embedded in the metal ligament to make the porous structure strong.

Referring to FIG. 3, one embodiment of a method for making thethree-dimensional porous composite structure comprising the followingsteps:

S10, providing a salt solution of inert metal and a salt solution ofactive metal;

S20, forming a first plating film by electroplating the salt solution ofinert metal on a substrate;

S30, placing a carbon nanotube structure on the first plating film;

S40, forming a second plating film by electroplating the salt solutionof active metal on the carbon nanotube structure; and removing thesubstrate to obtain a composite structure;

S50, annealing the composite structure formed in the step S40 at a hightemperature to obtain a preform structure;

S60, etching the preform structure to obtain a three-dimensional porouscomposite structure.

In step S10, the inert metal material can be selected from a groupcomprising copper (Cu), silver (Ag), platinum (Pt) and gold (Au). Theactive metal material can be selected from magnesium (Mg), aluminum(Al), zinc (Zn), iron (Fe), tin (Sn) and nickel (Ni). Compared with theinert metal, the active metal is very easy to react with acid and alkalisolution. Further, the salt solution of inert metal is sufficientlymixed with glucose, which can refine the following the first platingfilm. In one embodiment, the salt solution of inert metal is ZnSO₄, thesalt solution of active metal is CuSO₄.

In step S20, the substrate can be made of pure metal material or metalalloy. The metal material or the metal alloy is not limited. Examples ofthe metal material can be titanium (Ti), silver (Ag), platinum (Pt) andaurum (Au). A method for forming the first plating film includes thefollowing sub-steps:

S21, providing an inert metal plate used as a counter electrode, andusing the substrate as a working electrode;

S22, providing a certain voltage between the substrate and the inertmetal plate to form the first plating film.

In step (S21), the inert metal plate can be made of inert metalmaterials.

In step (S22), inert metal ions in the salt solution of inert metal getelectrons to form metal atoms, and the metal atoms are deposited onsurface of the substrate to form the first plating film. The firstplating film is located on surface of the substrate.

In step S30, the carbon nanotube structure includes at least one carbonnanotube film. The at least one carbon nanotube film is sequentiallylaid on the first plating film. The carbon nanotube film includes aplurality of successive and oriented carbon nanotubes joined end-to-endby van der Waals force therebetween. When the carbon nanotube structureincludes a plurality of carbon nanotube films, the plurality of carbonnanotube films can be coplanar or stacked. Adjacent carbon nanotubefilms are set at a certain angle.

A method for obtaining the carbon nanotube film is not limited. In oneembodiment, a method of making the carbon nanotube film includes thesteps of:

S31: providing an array of carbon nanotubes; and

S32: pulling out at least one carbon nanotube film from the carbonnanotube array.

In step S31, the carbon nanotube array is grown on a growing substrateby chemical vapor deposition. The carbon nanotube array includes aplurality of carbon nanotubes. The carbon nanotubes in the carbonnanotube array are substantially parallel with each other andperpendicular to the growing substrate.

In step S32, the carbon nanotube film can be drawn by the steps of:

S32 a: selecting one or more carbon nanotubes having a predeterminedwidth from the array of carbon nanotubes; and

S32 b: pulling the carbon nanotubes to obtain carbon nanotube segmentsat an even/uniform speed to achieve a uniform carbon nanotube film.

In step S32 b, the carbon nanotube segment includes a number ofsubstantially parallel carbon nanotubes. The carbon nanotube segmentscan be selected by using an adhesive tape as the tool to contact thesuper-aligned array of carbon nanotubes. The pulling direction can besubstantially perpendicular to the growing direction of thesuper-aligned array of carbon nanotubes. More specifically, during thepulling process, as the initial carbon nanotube segments are drawn out,other carbon nanotube segments are also drawn out end to end due to vander Waals force between ends of adjacent segments. This process ofpulling produces a substantially continuous and uniform carbon nanotubefilm having a predetermined width can be obtained.

In step S40, A method for forming the second plating film includes thefollowing sub-steps:

S41, providing an active metal plate used as a counter electrode, andusing the structure formed in step S30 as a working electrode;

S42, providing a certain voltage between the structure formed in stepS30 and the active metal plate to form the second plating film.

During the electroplating process, active metal ions in the saltsolution of active metal get electrons to form active metal atoms. Alarge number of active metal atoms are deposited on the surface of thecarbon nanotube structure, and a small number of active metal atoms canbe deposited into the micropores between adjacent carbon nanotubes inthe carbon nanotube structure.

The composite structure includes the first plating film, the carbonnanotube structure and the second plating film, which are stacked witheach other. Further, a plurality of composite structures can be formedby repeating step S10 to S40. The plurality of composite structures arestacked. The first plating film is formed on the second plating film,and the carbon nanotube structure is located on the first plating film,and the second plating film is formed on the carbon nanotube structure.An arrange direction of the carbon nanotubes in the carbon nanotubestructure can be selected according to practical needs.

In step S50, the process of annealing the composite structure at hightemperature comprises: heating the composite structure at a hightemperature to melt the first plating film and the second plating film,which the inert metal atoms in the first plating film are mixed with theactive metal atoms in the second plating film to form a middlestructure; then annealing and cooling the middle structure to form analloy of the active metal and the inert metal. The preform structureincludes an alloy of the active metal and the inert metal and the carbonnanotube structure. The alloy of the active metal and the inert metal islocated on the surface of the carbon nanotubes and the micropores ofadjacent carbon nanotubes in the carbon nanotube structure. Further, thealloy of the active metal and the inert metal is located in the nodes ofthe carbon nanotubes joined end to end therebetween.

Different metal materials have different annealing temperature. Theannealing temperature can be controlled according to the type of themetal materials. By controlling the annealing temperature differentmetal atoms can be fully diffused. During the process of hightemperature annealing, both the inert metal and active metal growdirectly on the carbon nanotubes to reduce the contact resistancebetween the carbon nanotube structure and the alloy of the inert metaland active metal. An interface between the carbon nanotubes and thealloy is a coherent interface. The annealing temperature is equal to orgreater than 300° C. In one embodiment, the annealing temperature isabout 450° C.

In step S60, referring to FIG. 4 a, FIG. 4b and FIG. 5, the method foretching the preform structure can be electrochemical corrosion orchemical corrosion. The preform structure is immersed in a dilute acidsolution or dilute alkali solution. A plurality of pores are formed inthe preform structure, due to the active metal in the preform structureoccur chemical reaction with the dilute acid solution or dilute alkalisolution.

In one embodiment, an electrochemical corrosion method is used to etchthe preform structure, in which the size of pores can be easilycontrolled. The size and distribution rate of the pores are determinedby a ratio of active metal to inert metal, dilute acid concentration,dilute alkali concentration and length of etching time. The longer theetching time, the larger the size of pores. In another embodiment, thedilute acid solution is dilute hydrochloric acid, and the weightconcentration of the dilute hydrochloric acid is 0.05 mol/L. The size ofpores is about 1 μm.

After etching the preform structure, a plurality of pores are formed inthe preform structure. The three-dimensional porous composite structureis shown in FIG. 6 and FIG. 7. One part of carbon nanotube can beexposed through the plurality of pores, and another part of carbonnanotube can be located in the plurality of pores, and/or the otherspart of carbon nanotube can be covered with the inert metal.

The method for making the three-dimensional porous composite structureprovided by above embodiment, a de-alloying technology is used to obtainthe three-dimensional porous composite structure, a plurality of carbonnanotubes are embedded in the metal ligaments to improve conductivity,mechanical strength and stability of the three-dimensional porouscomposite structure, meanwhile increases the specific surface area ofthe three-dimensional porous composites; the interface between carbonnanotubes and inert metal is a coplanar interface, which eliminate thecontact resistance between carbon nanotubes and inert metals, andfurther improve conductivity of the three-dimensional porous compositestructure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may includesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A method for making a three-dimensional porouscomposite structure comprising: S10, providing a salt solution of aninert metal and a salt solution of an active metal; S20, forming a firstplating film by electroplating the salt solution of inert metal on asubstrate; S30, placing a carbon nanotube structure on the first platingfilm; S40, forming a second plating film by electroplating the saltsolution of active metal on the carbon nanotube structure; and removingthe substrate to obtain a composite structure; S50, annealing thecomposite structure formed in the step S40 at a high temperature toobtain a preform structure; and S60, etching the preform structure toobtain a three-dimensional porous composite structure.
 2. The method ofclaim 1, wherein a plurality of composite structure are obtained, theplurality of composite structure are stacked with each other.
 3. Themethod of claim 1, wherein the carbon nanotube structure comprises atleast one carbon nanotube film, the at least one carbon nanotube filmcomprises a plurality of successive and oriented carbon nanotubes joinedend-to-end by van der Waals force therebetween.
 4. The method of claim3, wherein a method for making the carbon nanotube film comprises: S31:providing an array of carbon nanotubes; and S32: pulling out at leastone carbon nanotube film from the carbon nanotube array.
 5. The methodof claim 4, wherein the carbon nanotube array comprises a plurality ofcarbon nanotubes, the plurality of carbon nanotubes are substantiallyparallel with each other and perpendicular to a growing substrate. 6.The method of claim 3, wherein the carbon nanotube structure comprises aplurality of carbon nanotube films, the plurality of carbon nanotubefilms can be coplanar or stacked.
 7. The method of claim 6, wherein anangle between adjacent carbon nanotube films is ranged from 0° to 90°.8. The method of claim 1, wherein a process of annealing the compositestructure at high temperature comprises: heating the composite structureat a high temperature to melt the first plating film and the secondplating film, the inert metal atoms in the first plating film are mixedwith the active metal atoms in the second plating film to form a middlestructure; and annealing and cooling the middle structure to form analloy of the active metal and the inert metal.
 9. The method of claim 1,wherein the high temperature is equal to and greater than 300° C. 10.The method of claim 1, wherein a method for etching the preformstructure comprises: immersing the preform structure into a dilute acidsolution or dilute alkali solution for electrochemical corrosion orchemical corrosion.
 11. The method of claim 10, wherein the dilute acidsolution is dilute hydrochloric acid, and a weight concentration of thedilute hydrochloric acid is 0.05 mol/L.
 12. The method of claim 1,wherein the three-dimensional porous composite structure defines aplurality of pores, wherein a size of the plurality of pores is lessthan or equal to 100 μm.
 13. The method of claim 12, wherein a size ofthe plurality of pores is about 1 μm.